I have TeXLive-2020 installed on my computer, and by running pdflatex on this simple code,


a & b\\ c & d

I get the expected output: a math array (see figure). Two-column math array, left column with fixed width

However, when I compile the same file using Overleaf, I get a different output, as shown in the second picture. Two-column array, left column with fixed width (but math wrongly displayed as text)

It appears that Overleaf is treating the fixed-width columns (introduced by the array package, column specification w) as paragraph columns (colspec p). What's going on? I thought Overleaf was using regular TeXLive…

I have already notified Overleaf about this, so I might answer this question myself in a few days, if they provide some explanation. In the meantime, does anybody have a clue?

  • 1
    Hi, Tom from Overleaf Support here. I'm afraid that as the fix in the package was made later than when we deployed our TeX Live 2020 compiler, we can't really help with this issue. You can add the newer array.sty into your project. We plan to deploy TeX Live 2021 later this year that will include the fix. I hope this helps explain.
    – yo'
    May 10 at 13:47
  • Thank you very much Tom! I understand
    – fudo
    May 10 at 14:28

This was a change (bug fix, essentially) in the array package.

The tools change log notes

2020-04-06  Frank Mittelbach  <Frank.Mittelbach@latex-project.org>

    * array.dtx (subsection{Implementing column types w and W}):
    Use \d@llarbegin and \d@llarendde so that cell is typeset by
    default in math mode inside array; the use of >{$} ... <{$}
    to make such a column text mode remains possible
    (gh/297)  --- this is a breaking change!

Overleaf's texlive 2020 is an early version of tl2020 without the latex updates as they are very conservative in when they update (with good reasons really)

They have

Package: array 2019/08/31 v2.4l Tabular extension package (FMi)

You can add the newer array.sty to your overleaf project.

  • Thank you very much! So I guess the problem will be solved with the adoption of TeXLive-2021 by Overleaf, right?
    – fudo
    May 10 at 13:01
  • @fudo yes, or as I say you can upload the package into your project. The timing is a bit unfortunate, the w type was only added in the previous release and fixed soon after, hoping that not many people had used w in an array rather than a tabular by then, but the initial release has got locked for a year in overleaf, it happens.... May 10 at 13:04

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